Sexual reproduction & meiosis

• What are gametes in animals?

  Sperm and egg cells
• How many chromosomes do gametes contain?

  Half the number of normal cells
• What are normal cells with the full number of chromosomes called?

  Diploid cells
• What happens during sexual reproduction?

  One egg cell and one sperm cell combine
• What is the chromosome status of a fertilised egg cell?

  It is diploid
• What does the fertilised egg cell develop into?

  An embryo
• What is meiosis?

  A type of cell division
• How many gametes does meiosis produce from each parent cell?

  Four gametes
• What are the steps of meiosis?

  1. DNA in the parent cell is copied.
  2. The cell divides, each new cell gets half the chromosomes.
  3. Each cell divides again, pulling apart X-shaped chromosomes.
  4. Four new haploid gametes are produced.
• What does it mean for a gamete to be haploid?

  It has half the number of chromosomes
• Why is genetic variation important in offspring?

  It creates a mix of different variants
• What is the chromosome count of a haploid gamete if it has 12 chromosomes?

  12 chromosomes
• How many chromosomes will be in a fertilised egg cell formed by two haploid gametes with 12 chromosomes each?

  $24$ chromosomes
• What is the relationship between genes and characteristics?

  • Many characteristics are controlled by genes.
  • Most characteristics are controlled by more than one gene.
• What are alleles?

  Different versions of a gene
• How do chromosomes come in pairs?

  They have alleles of the same gene
• What happens if two alleles are different?

  The dominant allele shows, recessive remains
• When is the recessive allele shown?

  When there are two copies of it